Atomic sensors, such as nuclear magnetic resonance (NMR) gyroscopes and atomic magnetometers, employ optical beams to operate, such as to detect rotation about a sensitive axis or to detect the presence and magnitude of an external magnetic field. As an example, an NMR sensor system can employ a first optical beam as a pump beam and a second optical beam as a probe beam. For example, the pump beam can be a circularly-polarized optical beam that is configured to spin-polarize a vapor, such as cesium (Cs) or rubidium (Rb), within a sealed vapor cell of the sensor. The magnetic field can be generated by a magnetic solenoid to induce precession of alkali metal isotopes. The interaction between the polarized alkali metal vapor and the nuclear spin isotopes in the vapor cell gives rise to an effective magnetic field experienced by the nuclear spin isotopes based on the alkali number density and alkali fractional polarization. The greater the product of alkali number density and alkali fractional polarization, the greater the alkali magnetic field experienced by the nuclear spin isotopes.